I. Field of the Invention
This invention relates generally to a locking mechanism for telescoping extendable pole segments and more particularly to an improved internal cam mechanism which, upon a quarter turn of one pole segment relative to the other, with only a modest force, the two pole segments become rigidly locked together against relative longitudinal movement.
II. Discussion of the Prior Art
There are many applications where it is advantageous to have an extendable pole so that the overall length of the pole assembly can be adjusted. For example, the legs on a camera tripod may comprise two or more telescoping tubular segments whereby the height of the camera above ground can be adjusted by extending or retracting inner tubular pole segments relative to an outer segment. Likewise, in fruit picking or tree trimming applications, one may wish to provide a telescoping pole wherein the segments are collapsed relative to one another during storage but extendable when it is desired to reach a branch which is at a height greater than the length of the collapsed pole assembly. Once the desired length is reached by extending the inner pole segment relative to the outer pole segment, it often is desirable to lock that longitudinal adjustment. It is also desirable that the locking maneuver be simple and quick to accomplish with a minimum of fumbling.
In one prior art arrangement, the outer and inner tubular pole segments are provided with a series of apertures and when a desired extension length has been arrived at, it is necessary to insert a pin through the aligned apertures to maintain the overall length setting.
In applicant's co-pending application Ser. No. 07/280,124 filed Dec. 5, 1988, now U.S. Pat. No. 4,899,849, there is disclosed a ladder stabilizing assembly in which a pair of extendable, tubular, telescoping legs are hinged to the ladder's side rails and can be deployed to inhibit any tendency for the ladder to tip or slide. The telescoping legs includes a cam lock arrangement in which an eccentric disk secured to the inner tubular leg creates a wiping interference fit relative to the outer leg when the inner leg is rotated. The achieved locking force is primarily dependent on how much twisting force the user can impart between the two tube segments. The present invention comprises an improvement over that earlier arrangement for releasibly locking two tubular pole segments, one to the other, where the locking force is a large multiple of the force needed to engage the lock.